The invention relates to a method for carrying out epitaxial growth from the vapor phase of layers of semiconductor materials on semiconductor substrates, in a chamber being mainly constituted by a tube containing a susceptor for the substrate, in which tube gaseous compounds are circulated from one end to the other at a pressure and a temperature suitable to obtain the epitaxial growth of monocrystalline layers on the substrate.
The method is used in the manufacture of discrete components, such as: semiconductor lasers, photodiodes, photocathodes, field effect transistors, bipolar heterojunction transistors and in the formation of integrated circuits joining together one or several types of these components.
The manufacture of epitaxial layers from the vapor phase of materials of the group III-V is described in the magazine ACTA ELECTRONICA Feb. 21, 1978. The article of L. Hollan entitled "La croissance epitaxiale de GaAs en phase vapeur", p. 117-127, and the article of J. P. Hallais entitled "Croissance epitaxiale de semiconducteurs III-V a partir de composes organometalliques et d'hydrures", p.129-138, give information in the first place about the formation of epitaxial layers on substrates of GaAs from the vapor phase of chlorides and in the second place about the formation of such layers from the vapour phase of organometallic compounds. Other articles in the same magazine describe the use, of indium phosphide and gallium nitride.
The methods generally used have in common the introduction into a reactor of gaseous compounds from which the growth from the vapour phase takes place. This reactor generally has the form of a tube of quartz. The substrates are disposed in the tube on a sample carrier or a susceptor. The monocryatalline layers grow on the substrates upon the passage of the gaseous compounds. The aforementioned prior art documents state (p.132) that the rate of deposition essentially depends upon the composition of the flow of gas, but does not depend upon the deposition temperature. It should be noted (p.130) that in the method using organometallic compounds, reactors having cold walls are recommended.
In the field of semiconductor devices manufactured from compounds of the III-V group, the quality of the epitaxial layers is of major importance for obtaining a high manufacturing efficiency.
Since the semiconductor devices manufactured from materials of the III-V group are assumed to become of increasing interest in the future, attempts are made to improve the quality of the layers, of which these devices are made, in order to facilitate the manufacture of the devices.
These layers produced according to the technique of the prior art are generally not of uniform thickness. It has been found that the layers obtained by epitaxy from the vapor phase are thicker on the side on which the flow of gas enters into the reactor chamber than on the side on which it leaves this chamber. Moreover, it has been found that the rate of growth not only is not constant along the whole axis of the sample but that also the reduction of this rate is not linear. The curve of the rate of growth drawn as a function of the distance measured along the axis of the sample parallel to the flow of gases is a falling curve whose slope falls uniformly.